The news of his death came as the number of confirmed cases in the Edinburgh area rose from seven to 17 within just a few hours yesterday.

In a normal year, NHS Lothian expects to see just five cases.

Health chiefs said that 14 men and two women aged between 33 and 74 were in a critical condition last night in intensive care units across the area.

I would like to reassure the public that household water supplies are safe and that legionnaires’ disease cannot be contracted by drinking water

Dr Duncan McCormick

One man recovered and was discharged.

NHS Lothian bosses are also investigating 15 suspected cases across Edinburgh. Samples have been taken from four cooling towers in the south-west of the city, though it may be up to 10 days before results are available.

Those responsible for maintenance at the cooling towers have been advised to carry out additional chemical treatment to the water in the cooling systems as a precautionary measure, but the health board said other possible sources are not being ruled out.

Further inspections will be made by Environmental Health officers, scientists and the Health and Safety Executive to ensure control measures are being carried out effectively.

The majority of the cases have been linked to the Dalry, Gorgie and Saughton areas of the city.

Dr Duncan McCormick, consultant in public health medicine and chair of the Incident Management Team, said: “I would like to express my sincere condolences to the family of the patient who died. Investigations into the possible source of this outbreak are ongoing. Meanwhile, medical staff have been identifying possible cases to allow us to ascertain the full extent of this outbreak.

“I would like to reassure the public that household water supplies are safe and that legionnaires’ disease cannot be contracted by drinking water.”

Bacteriology expert Professor Hugh Pennington said: “Essentially it is a preventable disease. Industrial water cooling towers are quite a common source of the bug. The bug lives in warm, fresh water. Basically what should be done is disinfectant should be put in the water to stop the bug growing.

“Clearly that hasn’t happened and the aerosol of water that comes out of these cooling towers contains the bug, people breathe it in and then they get legionnaires’ disease, which is essentially a very, very severe pneumonia.”

The first case was identified last Thursday.

The symptoms of legionnaires’ disease, which include fever, chills, and a cough, can begin any time from two to 14 days after first exposure to the bacteria.

NHS Lothian urged anyone who develops symptoms to contact NHS 24 or go to their GP.

It comes just a year after NHS Greater Glasgow and Clyde Public Health Protection Unit launched an investigation after an “unusual” rise in the number of cases of legionnaires’ disease in Glasgow.